Need some help to understand why my program isn't working as expected.

Here's the breadboard view of my circuit. Basically a ATtiny85 with PB1 hooked to a 4-legged PCB-mount push-button switch, with a 10K pull-down resistor to GND, s.t. when button is pressed PB1 is pulled HIGH, else LOW. Also PB4 is hooked to an LED via a 470R. Only other thing connected to the IC is Vcc and GND.

The current behavior is that the LED is always on, while it was supposed to be normally off, and turn-on only when button is pressed. Here is my code. What is it that I am doing wrong --